When using a camera equipped borescope to inspect engines or machined parts for imperfections of interior surfaces, it would be advantageous to be able to perform and record accurate, three-dimensional measurements to obtain the dimensions of the imperfections in order to be able to evaluate the extent of the damage and to determine what corrective measures should be taken.
During endoscopic medical procedures, it is of an advantage to perform accurate three dimensional measurements to obtain dimensions of anatomical structures within the lumen, such as lesions, stenoses, tumors, and the like. Tracking such measurements along time may further improve the level of care provided.
For example, Otorhinolaryngologists may benefit from recording the dimensions, opening, and alignment of patients' vocal cords. Pulmonologists can quantify airway size and establish treatment protocol accordingly. Monitoring these data provides valuable information related to effectiveness of a treatment, disease progression and the like. Another example is monitoring the size of polyps in the gastrointestinal tract or the stomach, to support further treatment decisions.
Currently, physicians using a state of the art endoscope, be it flexible or rigid, monocular or stereoscopic, do not have a true volumetric perspective within the acquired image and are unable to conduct accurate measurements. A common practice is to place an object of known size (e.g., a catheter with known diameter) next to the anatomical structure and use it as a scale to assess dimensions.
The actual necessity of obtaining accurate 3D measurements during endoscopic procedures is manifested by several patents and patent applications, describing inventions aimed at providing a solution to the problem. Some of these patents and applications are registered to key vendors in the medical devices arena, such as Olympus, Toshiba, Covidien and others. Most of the state of the art (issued patents and applications) attempts to obtain a full depth image of the endoscopic field of view. Additionally, several vendors are promoting stereoscopic endoscopy to answer complementary needs.
In U.S. Pat. No. 5,090,400, ‘Measuring Endoscope’, issued to Toshiba on Feb. 25 1992, the use of a laser pattern generated at the end of a fiber by a standard diffraction grating is synchronized with the illumination light for observation.
In U.S. Pat. No. 5,784,098, ‘Apparatus for Measuring Three-dimensional Configurations’, issued to Olympus on Jul. 21 1998, an oscillating structured light and beam splitters are used to measure the 3D configuration of an object.
In U.S. Pat. No. 8,248,465, ‘Measuring Endoscope Apparatus and Program’, issued to Olympus on Aug. 21 2012, two images combined with triangulation on image data is used to generate the measurements.
In U.S. Pat. No. 8,496,575, ‘Measuring Endoscope Apparatus, Program and Recording Medium’, issued to Olympus on Jul. 30 2013, a system that includes an endoscope and a processing section that measures distances on two images received from the endoscope based on a triangulation method.
U.S. Pat. No. 8,558,879, ‘Endoscope Apparatus and Measurement Method’, issued to Olympus on Oct. 15 2013, further describes an apparatus and method, which is partly manual in nature, requiring the user to mark correspondence points in both images.
U.S. Pat. No. 8,465,415, ‘Endoscope Apparatus and Measurement Method’, issued to Olympus on Jun. 18 2013, takes a different approach, by measuring a shake in an interlaced image to generate a second image that is measurable.
There are yet other approaches to providing a solution to the problem, for example:
In U.S. Pat. No. 7,740,578, ‘Direct reading endoscopic measuring instrument and method’, issued to Paul K. Little on Jun. 22 2010, the invention relates to a physical reticule which is extended from the distal end of the endoscope and placed proximate to an anatomical structure to be measured, and then retracted accordingly.
In CN 2,689,888Y, ‘Measuring type endoscope biopsy forceps’, Apr. 6 2005, the inventors use color coded graduation marks to assess the extent of disease.
Additional background information may be found in the following patent applications: US2004/0242961 (corresponding to EP1480067A1), US2009/0225321, US2012/0289778, US2014/0028819, WO2005/027739A1, WO2012/147679A1, EP2106748A1, EP2160974A1, EP2630915A1 and in a paper published in ‘Lasers in Surgery and Medicine 45:377-382 (2013—http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3791553/)’, titled ‘Proof-of-concept of a Laser Mounted Endoscope for Touch-Less Navigated Procedures’, which emphasizes the need for measuring 3D data in adjacent domains.
Further research includes ‘Calibration of laryngeal endoscopic high-speed image sequences by an automated detection of parallel laser line projections’ by T. Wurzbacher et al., Medical Image Analysis 12 (2008) 300-317, where two parallel planes of known distance, mounted on a rigid endoscope, generate two intersection curves with the vocal cords that are approximated as straight lines, and are merely used for coarse scaling of image pixels. Another research article titled ‘Depth-kymography: high-speed calibrated 3D imaging of human vocal fold vibration dynamics’ by N. A. George et al., Phys. Med. Biol. 53 (2008) 2667-2675, describes a rigid endoscope equipped with a laser projection channel that uses a large triangulation angle and a specific calibration method to enable highly accurate vertical measurement of the front surface of the vocal folds, as they vibrate in low amplitude. Both of these setups are inapplicable for measuring lumens with a large depth of field, and therefore are unsuitable for providing 3D measurements in general.
To the best of the inventor's knowledge, no commercially available medical endoscope to date has the capability to accurately take 3D measurements and to record them. Furthermore, the state of the art solutions for three-dimensional endoscopy are mostly complex. In some, the device includes a complex assembly of mechanical, electrical and optical components. In others, such as Olympus iPLEX stereoscopic borescope, the measured object must have salient features and the required extra user interaction renders the process cumbersome.
It is noted that the terms “endoscope” and “endoscopic device” are used herein in a generic sense to apply to endoscopes, catheters, laparoscopes, and similar instruments used in medical applications and also to borescopes and similar instruments used in non-medical applications.
It is therefore a purpose of the present invention to provide a system and a method capable of making accurate 3D measurements of objects observed in the field of view of an endoscopic visualization system.
It is another purpose of the present invention to provide systems capable of making accurate 3D measurements of objects observed in the field of view of an endoscopic visualization system that is structurally much less complex than existing systems.
It is another purpose of the present invention to provide a method capable of making accurate 3D measurements of objects observed in the field of view of an endoscopic visualization system that is structurally much less cumbersome to carry out than existing methods.
Further purposes and advantages of this invention will appear as the description proceeds.